Ch06.1 - The steady state of an enzyme-catalyzed reaction is reached when A.the rate of appearance of product over time is constant B.the rate of

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The steady state of an enzyme-catalyzed reaction is reached when A. the rate of appearance of product over time is constant. B. the rate of enzyme-substrate formation is constant. C. the concentration of enzyme-substrate complex equals the concentration of product. D. the concentration of the enzyme-substrate complex is constant over time.
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Enzymes (Ch. 6) 1. Kinetics
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Enzymes are highly specialized proteins with several impt features: 1. Extraordinary catalytic power – typically accelerate reactions by factors of at least a million. e.g. hydration of CO 2 is catalyzed by carbonic anhydrase: CO 2 + H 2 O H 2 CO 3 Each enzyme molecule can hydrate 10 5 molecules CO 2 per sec. = 10 7 times faster than uncatalyzed reaction! 2. High degree of specificity - e.g. can tell difference between L and D isomers 3. Catalyze reactions without formation of byproducts 4. Work under mild conditions of temp and pH - e.g. nonenzymatic hydrolysis of proteins typically requires 6 M HCl at 110 °C; protease trypsin acts at neutral pH and 37 °C.
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Louis Pasteur (1850’s) Proposed fermentation of sugar into alcohol by yeasts catalyzed by "ferments". Later named enzymes ( in yeast ) - postulated that they were inseparable from structure of living yeast cells. Landmarks in enzymology:
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6-1 •Why enzyme catalysts so large compared to substrates? •How can aa, which can’t themselves accelerate rxns, produce such powerful catalytic activity when linked in specific sequences? •How is enzyme activity regulated?
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Catalysis = enhancing rate of specific chemical reaction that would otherwise occur very slowly Catalysts do not change equilibrium point, but simply increase rate at which equilibrium is reached The catalyst is not used up or permanently altered
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Catalyst lowers activation energy of the transition state Activation energy of catalyzed reaction Transition state Activation energy of uncatalyzed reaction Where is the transition state?
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Rate of any reaction is proportional to concentration of transition-state species, X : S X P Two ways to increase proportion of molecules with transition-state energy:
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This note was uploaded on 11/02/2009 for the course CH 302 taught by Professor Holcombe during the Spring '07 term at University of Texas at Austin.

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Ch06.1 - The steady state of an enzyme-catalyzed reaction is reached when A.the rate of appearance of product over time is constant B.the rate of

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